The invention concerns a heating device for a fluid line, preferably for a gas fluid line, in particular for a venting line of a crankcase of an internal combustion engine.
Heating devices for fluid lines are widely known in plant construction and are used in particular in internal combustion engines in order to heat liquids or gases in ducts to a predetermined temperature level. For example, inter alia heating devices for urea water solutions for diesel injection systems are known, but also heating devices for blowby gases of a crankcase venting device.
In internal combustion engines blowby gases occur which are produced in that combustion gases in the cylinder flow past the cylinder piston into the crankcase. These blowby gases that contain uncombusted hydrocarbons cause an increase of pressure within the crankcase and this may lead to leakage and escape of oil. In order to avoid a pressure increase and in order to discharge the blowby gases in an environmentally friendly way, they are returned from the crankcase into the air intake manifold of the internal combustion engine. Due to the high pressure differences between crankcase and air intake region, the gases generally cool down and there is the risk of condensation, wherein dirt particles deposit in the air intake manifold and cause soiling. For this reason, heating devices are employed in the venting valves or in the crankcase venting lines wherein, by means of a PTC element (positive temperature coefficient element—thermistor) the returned gases are heated to a desired temperature. PTC elements are comprised in general of a semiconductive polycrystalline ceramic, for example, barium titanate, that are ready-made in a disc or plate shape and are supplied with electric current by means of metallic contact elements. Such heating devices in general comprise a pipe or duct segment of thermally conductive material, for example, copper, aluminum or steel, through which the fluid to be heated can flow, wherein the pipe segment is coupled with an electrical heating element for heating the pipe segment. The electrical heating element is in general connected by an electrical plug connection device with the electric power supply of the internal combustion engine.
The prior art discloses heating devices which are in part sealed against aggressive blowby gases wherein a heating element is soldered onto a pipe segment or is glued on by means of a heat-conductive adhesive. Moreover, it is known to attach by injection-molding an electrical plug connection device to the pipe segment wherein the heating element as well as its electrical contacts are pressed by means of a spring force onto the pipe segment. Finally, shrunk-on heating elements or pressed-in or caulked heating elements on a pipe segment are known that are embedded in a plastic housing by injection molding.
DE 10 2007 026 805 A1 discloses a heating device wherein a heating element on a pipe segment is embedded by injection molding in a plastic housing and multi-layer lamination sealing rings are arranged for sealing on the two axial ends of the pipe segment. The heating element is fused by means of the plastic housing immediately onto the pipe segment.
EP 1 772 613 A1 discloses a heating device in which a heating element is pressed by a contact spring onto a pipe segment wherein the contact spring is fused within a plastic housing and is formed with a plug connection device.
In addition, DE 103 26 894 B3 discloses a heating device which can be attached like a clamp about a duct. The heating element is encapsulated in a plastic housing on an axial projection of the wrap-around clamp wherein the heating element is pressed onto the heat-conductive projection of the pipe clamp.
Based on the aforementioned prior art, it is the object of the invention to propose a heating device that enables a simple manufacture, offers an improved insulation relative to blowby gases, and provides a high electrical and thermal contacting quality.